You obviously don't really forget how to play the old songs; you just don't have to spend so much time convincing yourself that you remember them. Way less mental energy is spent swimming around in lyrics you've already written and chords you've already played.

Stop trying to treat music like it's a tennis shoe, something to be branded. If the music industry wants to save money, they should take a look at some of their six-figure executive expense accounts. All those lawsuits can't be cheap, either.